OXIDATION OF HYDROGEN AND CARBON. 6 1 



(63.) I have here an ordinary form of apparatus in which 

 hydrogen gas is being generated in the usual manner from zinc 

 and dilute sulphuric acid, and dried by transmission through oil 

 of vitriol. On burning the jet of dried hydrogen under this cold 

 bell jar, we observe that the interior of the jar becomes quickly 

 covered with a film of condensed steam or water, produced by 

 the direct combination of the hydrogen gas with the oxygen of 

 the air ; and, by properly contrived experiments, I might show 

 that the weight of water produced in this way is exactly equal 

 to the weight of oxygen and hydrogen' consumed in the burning. 

 But during the combustion of the gases there is a production not 

 only of water, but of heat ; which I may exhibit to you in a 

 more striking manner. We have here a piece of clean platinum 

 foil, which is now maintained in a state of ignition by the hydro- 

 gen flame. I turn off the supply of hydrogen for a minute or so, 

 and before the platinum has become quite cold, turn it on again, 

 when you observe that the metal becomes and continues feebly 

 red-hot without inflaming the gas. The mixed hydrogen and 

 air on the surface of the foil combine with one another to form 

 water, and at the same time produce an amount of heat sufficient 

 to maintain the metal in a state of visible ignition. But where 

 does this heat come from ? We have a production of heat and a 

 production of water; ought we not to account for the one as 

 intelligibly as we do for the other ? 



(64.) I now take a piece of charcoal, and make it red-hot in 

 the Bunsen gas flame. Having first poured a little lime-water 

 into the bottle of oxygen, to show the result of the action, I 

 next introduce the glowing charcoal, when combination between 

 the gas and charcoal takes place, you perceive, with vivid com- 

 bustion. In this experiment, then, we have carbonic anhydride 

 or di-oxide of carbon formed, the source of which is perfectly 

 evident ; and upon shaking up the resulting gas with the clear 

 lime-water we previously poured into the bottle, that which was 

 soluble hydrate of calcium becomes insoluble carbonate of cal- 

 cium or chalk, whereby we have as you see, a considerable 

 white turbidity produced, thus : 



